1st runs this weekend on the 498 in my 70 chevelle.the is 3200 lbs with me.glide, 6000 stall. 488 rear, all the same as the 468. car is only running 133to 134 mph on the throttle stop for 10.90. the weather has something to do with it ;mid 90's with 70 % humidity at topeka. maybe 3 mph more at most than the 12 to one 468 that was in the car for the same conditions. i expected 136-7 and 140 in perfect weather. 13 to 1 498 ,279 286 749 on 110 4 deg advanced same brodix 320 cc heads that were on the 468 freshened up . flow 370 and 305 @ 700 dr j ported 454r intake. 2 circuit 1050 annular. 2.125 headers with 3.125 to 4 in merge collector and about 15 in collector length from the smallest diameter to the end. headers might be too small for this engine and too much collector length. tried timing adjustments and ended up at 38 degs. its a little rich still but should be close. should have ran it on a dyno but needed to get it in. any ideas?gnicholson Member

the convertor was a little tight with the 468 so i left it alone. stalls about 6000. i think a little looser would pick it up but dont want to over rev it. on the stop 60 ft times were 1.86 to 8 ,maybe a hair quicker. i need to get the slips for the rest of them but a few hundreths faster on all the increments as far as i can tell

thanks. the convertor stalls maybe 100 rpm more. the cam in the 468 was 272 278 708 on 112 so the one in this engine is bigger at 279 286. the stop still goes to 4000 rpm against the convertor. i checked that in mid 90 deg weather.

Hummm, Yeah I'd say those heads might be a problem or sorts. My 18* SBC Dart heads flow that much on the intake side. 254 on the exhaust. That engine is making close to 800hp on a good day.

X2 and I am with Ken on this one, I also think the heads are holding it back as I have the Dart 325's and I have changed from an 1150 to a 1250 thinking it would pick up some but nope!!! my heads are what they are and for another $1200. I can gain 2 more tenths, but I am going to spray my engine next year so I will see what kind of gains I can make with it.

My heads flow a tad over 370 on the intake side and I can feel the engine and it is just maxed out for air. I run a 505 inch engine and buzz to 7900 at the stripe and that is just about all it has at that point and my cam is less than .800 lift. My 2 cents.

You may have 370 cfm flow but your not making power from it. the flow quality would be junk, turbulent city, uneven flow cones all that stuff. 370 cfm is enough to make 870hp average on any day or weather on a 412 provided the flow is nice and even around the valve, nice cone, no turbulence etc. But your 498 engine is pulling on the port too hard probably. its not making the HP per cube, its making stuff all really. Suggest getting much better heads.